Sudden apnea in a child’s sleep may be due to the baby being born prematurely, or it may be caused by obstruction of the upper respiratory tract and abnormalities of the respiratory center. 1. Preterm babies may experience a brief respiratory pause of about 5 seconds and then return to a normal breathing rhythm. This phenomenon is called periodic respiration, usually occurs in infants less than 6 months, may be caused by the infant respiratory system is not yet well developed, such as episodes are infrequent, can be temporarily observed and followed up treatment. If necessary, ventilation can be assisted by ventilator. 2. If the apnea exceeds 15 seconds in full-term infants, 20 seconds in preterm infants, or if the apnea does not reach the above length, but there are symptoms of hypoxia, such as slow heart rate and skin bruising, it is regarded as sleep apnea. Sleep apnea is categorized into obstructive sleep apnea, central sleep apnea and mixed sleep apnea. Obstructive sleep apnea is the most common, in which airflow from the mouth and nose stops, but breathing movements are present. Obstructive sleep apnea can be caused by adenoid and tonsil hypertrophy, nasal polyps, tongue root fall back and other diseases that cause upper airway obstruction. Central sleep apnea is characterized by cessation of airflow from the mouth and nose without respiratory movements. It is not related to the obstruction of the airway, but to the dysfunction of the respiratory center of the brain, and is most often seen in the possibility of brain injury. Mixed sleep apnea is a mixture of obstructive and central sleep apnea. Prolonged hypoxia can affect growth and development, complicate pulmonary edema and cardiac arrhythmia, etc. Therefore, if sleep apnea is diagnosed, it needs to be actively cooperated with the treatment.